The invention relates to art conservation. More particularly, the invention relates to sonic systems for determining the condition of frescos and similar murals.
A fresco mural (e.g., painting or mosaic) is a painting made on a masonry wall by brushing pigment-water mixtures into a fresh plaster layer, or by inlaying small pieces of colored glass, stones, or other materials into a fresh plaster layer. Fresco murals have endured thousands of years.
The interiors of the U.S. Capitol buildings have many fresco paintings, each over 100 years old, many in need of substrate repair. See, Barbara A. Wolanin, “Constantino Brumidi: Artist of the Capitol” (U.S. Government Printing Office, Washington, D.C., 1998). A similar situation exists in buildings of the Vatican and in other Italian locations and other locations near the Mediterranean Sea.
An exploratory technique has been used to evaluate fresco substrates by using a loudspeaker system to direct sound waves toward the fresco mural and a laser interferometer vibration sensor to measure the resulting motion of many locations of the mural. A sound pressure level of 90 to 100 dB is needed to obtain enough motion to measure, but makes the location near the painting too noisy for normal use. See, J. Vignola, J. Bucaro, J. Tressler, D. Ellingston, A. Kurdila, G. Adams, B. Marchetti, A. Agnani, E. Esposito, E. P. Thomasini, “Proper Orthogonal Decomposition Analysis of Scanning Laser Doppler Vibrometer Measurements of Plaster Status at the US Capitol”, 6th Int. Conf. on Vibration Measurements by Laser Techniques, Proc. SPIE Vol 5503. See, also, U.S. Pat. No. 6,728,661 of Cannelli et al., identifying use of a wideband acoustic detector.